Glass glazing can be substituted with transparent materials, such as plastics, which do not shatter or are more resistant to shattering than glass. For example, transparent materials made from synthetic organic polymers are utilized in public transportation vehicles such as trains, buses, taxis and airplanes. Lenses for eye glasses and other optical instruments, as well as glazing for large buildings, can also employ shatter-resistant, transparent plastics. Additionally, the lighter weight of these plastics in comparison to glass can be a further advantage, especially in the transportation industry where the weight of the vehicle is a major factor in its fuel economy.
While transparent plastics provide the major advantage of being more resistant to shattering, lighter than glass, and having design flexibility, a serious drawback lies in the ease with which these plastics mar and scratch due to everyday contact with abrasives such as dust or cleaning equipment. Marring results in impaired visibility and poor aesthetics, and often requires replacement of the glazing or lens or the like.
To improve the abrasion resistance of plastics, mar-resistant coatings have been developed. The main disadvantage of these abrasion resistant compositions is that they may not be formable after curing. Poor formability means that bending or working a coated article will often lead to cracking or crazing of the coating. As a consequence, articles must be coated after forming, which may entail time delays and shipment of uncoated articles which may be inadvertently abraded in transit.
Additionally, it is often desired to provide tintable coatings that possess abrasion resistance. In particular, these coatings can be useful for tinted window applications and for ophthalmic applications. Many known coating compositions do not readily allow for a tint to be added to the coating composition after the coating composition has cured on the substrate. The ability to add a tint to such a cured coating composition is highly desirous.
Thus, there remains a need in the art for coatings having good abrasion resistance and formability. In addition, there remains a need in the art for coatings exhibiting abrasion resistance and tintability.